95 gt. Runs great most of time. But on hot days it will suddenly start loosing power to the point it seems to be missing very badly. If you finally get it to crank back up it will run for a few seconds them start missing again. Dist, coil, ignition module all have been replaced. The fuel pump is clicking on when key is in run position. I had to get it towed today. In the past, the next day it will run good again. I never know when it's going to leave me stranded. Any ideas? Thanks in advance
Need Help Shuts Down When Hot
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jozsefsz
15 Year Member
Check fuel pressure when it's acting up. What kind of distributor did you use for the replacement? It's not uncommon for various remans to change the bushing but leave a faulty PIP in place. Removing the SPOUT connector when it's not starting can help determine if that's the cause (it'll sometimes allow the engine to start and run). It's almost always one of the things you mention have all been replaced, or if it's tuned / modified in some fashion and the closed-loop tune is way off, that doesn't show up until warm. If it's not throwing any codes (pull codes) then it's even more likely it's one of the big 2 (pip, TFI module).
jozsefsz
15 Year Member
I don't believe you'd be able to retain the factory computer without a stock distributor setup -- the tach would be the least of your worries. The PIP signal tells the computer when the engine is running (and to run the fuel pump), and the injectors also fire based on its signal. You'd need to go to a carb to use this distributor. Personally I'd try my luck with another distributor - hopefully you have a warranty.
Today i put in a brand new dist not reman. New ign module replace and it still has the same problem. This makes two sets of replacements. I no longer think any ignition component is the problem. Checked fuel pressure at fuel rail its 30psi at idel
Let me run this by you give me your opinion. This seems to only happened with the engine hot from driving a few hours on a hot day of over 90 degrees in the southern states. My girl and I went for a drive to the mountains drove for several hours not one problem. We drove it on a hot day problem back again. I did a search on vapor lock on sn95 mustangs. What I found was people saying that vapor lock usually don't happen in fuel injection cars because the fuel return line allows fuel to keep flowing thru the lines over hot engines and this allows fuel to stay cooler. But if the return line gets clogged vapor lock can happen.
Lmr sells a stainless return line kit for 144 bucks. Are there anyway to test this theory? Thanks.
Let me run this by you give me your opinion. This seems to only happened with the engine hot from driving a few hours on a hot day of over 90 degrees in the southern states. My girl and I went for a drive to the mountains drove for several hours not one problem. We drove it on a hot day problem back again. I did a search on vapor lock on sn95 mustangs. What I found was people saying that vapor lock usually don't happen in fuel injection cars because the fuel return line allows fuel to keep flowing thru the lines over hot engines and this allows fuel to stay cooler. But if the return line gets clogged vapor lock can happen.
Lmr sells a stainless return line kit for 144 bucks. Are there anyway to test this theory? Thanks.
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jozsefsz
15 Year Member
I'm sorry PIP / TFI didn't do the trick, at least you have some spares now (in my experience the new ones definitely don't last 20 years like the factory parts, as the originals weren't made in China). You'd need to check the fuel pressure when it's acting up, as I'd suggested earlier, not just when it's running fine at idle. I had a pump go bad a few years ago that only messed up on hot days too. A good pressure reading would eliminate pump, fuel pressure regulator, problems with the return line, or any theoretical vapor lock.
It's unlikely as you'd read to have vapor lock with an in-tank pump (all push, no pull of fuel). If the return line were clogged you'd get very high fuel pressure. I don't think that's what's happening, but the fuel pressure reading when it won't run is your best test imho.
It could be something like a kinked evap line or something wrong with that system. Which, as fuel is used up, could cause a vacuum to build up in the tank. Or on really hot days it could cause pressure to build up. Either one could affect your fueling. If it starts acting badly again, you might try removing the fuel cap and see if you hear hissing (pressure) or if it's tough to remove (vacuum). If it starts up after you remove the cap then you're definitely onto something.
It's unlikely as you'd read to have vapor lock with an in-tank pump (all push, no pull of fuel). If the return line were clogged you'd get very high fuel pressure. I don't think that's what's happening, but the fuel pressure reading when it won't run is your best test imho.
It could be something like a kinked evap line or something wrong with that system. Which, as fuel is used up, could cause a vacuum to build up in the tank. Or on really hot days it could cause pressure to build up. Either one could affect your fueling. If it starts acting badly again, you might try removing the fuel cap and see if you hear hissing (pressure) or if it's tough to remove (vacuum). If it starts up after you remove the cap then you're definitely onto something.
I'm not familiar with the evap system. Will have to do some reading on that. Makes since on what you said about the pressure would increase on the fuel rails. My gauge is a portable test gauge type not a permanent one. But I may be able to tie it in place under the hood. But the only problem with this is that the engine usually dont run long enough for me to get out the car and look under the hood. Are there a cheep gauge and lines I could run to the inside of the car temporary?
jozsefsz
15 Year Member
I probably have the same type (autozone special 
). Just keep it in the car with you for the next time it does it (I don't like to keep it hooked up just in case it leaks from somewhere) Just priming the pump with a few turns of the key should give you enough information. Turn over the key, let the fuel pump buzz without starting the engine, a couple of times. Pressure should go up to about 40psi and stay there for a while before it drops back down (giving you enough time to jump out and take a look). If you're with a passenger even better, watch the gauge while they try to start the car.
). Just keep it in the car with you for the next time it does it (I don't like to keep it hooked up just in case it leaks from somewhere) Just priming the pump with a few turns of the key should give you enough information. Turn over the key, let the fuel pump buzz without starting the engine, a couple of times. Pressure should go up to about 40psi and stay there for a while before it drops back down (giving you enough time to jump out and take a look). If you're with a passenger even better, watch the gauge while they try to start the car.After I got home with the car and had installed the fuel pressure test gauge I turned the key on just the one time not doing it several times not cranking it and it only read around 5 to 8 lbs. It wasn't until I cranked the car that it went to 30 psi. But could be air in the test line. But I will look at that tomorrow before I crank it up since I still have it hooked up.
The temp sensor to the brain has been replaced. So not that. I'm still leaning toward vapor lock. Have had a few people tell me the same. They rerouted some fuel lines that were close to the engine to solve the problem.
jozsefsz
15 Year Member
Did you ever succeed getting some good fuel pressure readings? (note you have to turn the key more than once if it isn't running to get up to full pressure, especially if you just connected the gauge). Some guy up there ^ gave you quite a few good suggestions to eliminate the extremely unlikely possibility of vapor lock. It's not going to happen on an in-tank fuel-injected car due to the routing of the lines in the engine bay.
At this point with PIP & TFI replaced, I'd put good money on the fact that it's your fuel pump. But only you can put the gauge on it to find out for sure.
It's not going to happen on an in-tank fuel-injected car due to the routing of the lines in the engine bay. At this point with PIP & TFI replaced, I'd put good money on the fact that it's your fuel pump. But only you can put the gauge on it to find out for sure.
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